Malaysian police arrested a woman on Wednesday in connection with the death of North Korean leader Kim Jong Un’s half brother. Police released a statement saying the woman was carrying Vietnamese travel documents when she was arrested at Kuala Lumpur International Airport. Kim Jong Nam died Monday after suddenly falling ill at the budget terminal of Kuala Lumpur International Airport, said a senior Malaysian government official, who spoke on condition of anonymity because the case involves sensitive diplomacy.

Watch What Else Is Making News

Kim, who died on the way to a hospital, told medical workers that he had been attacked with a chemical spray, the official said. Malaysian officials have provided few other details. Police said an autopsy will determine the cause of death.

Since taking power in late 2011, Kim Jong Un has executed or purged a slew of high-level government officials in what the South Korean government has described as a “reign of terror.” South Korea’s spy service said today that North Korea had been trying for five years to kill Kim. But the National Intelligence Service did not definitively say that North Korea was behind the killing, just that it was presumed to be a North Korean operation, according to lawmakers who briefed reporters about the closed door meeting with the spy officials.

The South Korean National Intelligence Service (NIS) cited Kim Jong Un’s alleged “paranoia” about his half brother. Still, the agency has a history of botching intelligence on North Korea and has long sought to portray the country’s leaders as mentally unstable. Multiple South Korean media reports, citing unidentified sources, said Kim Jong Nam was killed at the airport by two women believed to be North Korean agents. They fled in a taxi and were being sought by Malaysian police, the reports add.

Police were searching for clues in the closed circuit television footage from the airport, said Selangor police chief Abdul Samah Mat. The airport is in Selangor, near Kuala Lumpur. According to the Malaysian government official, Kim Jong Nam was in a shopping concourse and had not yet gone through security for a planned flight to Macau when the incident occurred.

Kim was estranged from his half brother, the North Korean leader. Although he had been originally tipped by some outsiders as a possible successor to his late dictator father, Kim Jong Il, others thought that was unlikely because he lived outside the country, including recently in Macau, Singapore and Malaysia.

He reportedly fell further out of favour when he was caught trying to enter Japan on a false passport in 2001, saying he wanted to visit Tokyo Disneyland.

A Malaysian police statement confirmed the death of a North Korean man whom it identified from his travel document as Kim Chol, born in Pyongyang on June 10, 1970.